1. Technical Field
The present invention relates to a suspension device for vehicle rear wheels, and particularly relates to a suspension device for vehicle rear wheels configured to enable influence of longitudinal force compliance steer generated at an early stage of turning to be suppressed or cancelled out.
2. Related Art
A suspension device for rear wheels of a vehicle such as a vehicle or the like is configured to support hub bearing housings configured to turnably support a rear wheel, via a suspension link (link) pivotally attached to the vehicle body so as to able to stroke in the longitudinal direction.
Such a suspension device for rear wheels preforms, as an example, positioning in the camber directions of the rear wheels using longitudinal pairs of lateral links, and also performing positioning in the toe directions by disposing the pair of lower side lateral links in a manner separated forward and backward.
An example of such a suspension device for rear wheels is disclosed in Japanese Unexamined Patent Application Publication (JP-A) No. 2011-57021. This suspension device performs positioning of the hub bearing housings using front and rear lateral links (lower links) and trailing links pivotally attached to a sub frame to be attached to a rear underfloor of a vehicle body.
One or both end portions of each of these links are connected to the vehicle body or hub bearing housing via a rubber bush for vibration proofing. For example, in the case of lateral force being applied to a vehicle at the time of turning of the vehicle, there is generated lateral force compliance steer in which the toe angle of a rear wheel is changed to either of the toe-in and toe-out directions due to deformation amount difference between the rubber bushes of the front and rear lateral links.
In general, it is desirable that, at the time of turning of a vehicle, the turning outer wheel side has a tendency to toe in, and the turning inner wheel side has a tendency to toe out, and accordingly, rigidities of the rubber bushes of the front and rear lateral links are frequently set such that displacement amount as to lateral force is greater at the front side than at the rear side.
Also, the geometric layout (geometry) of the links making up the suspension may frequently apply bump steer properties such that the turning outer wheel side, that is, bump side (compressed side) has a tendency to toe in, and the turning inner wheel side, that is, the rebound side (expanded side) has a tendency to toe out.
However, in the case of a suspension exhibiting lateral force compliance steer such that, at an early stage of turning, according to lateral force at the time of turning as described above, the outer wheel side toes in, and the inner wheel side toes out, there may be exhibited a tendency in which, according to compliance steer (longitudinal force compliance steer) due to longitudinal force, the outer wheel side toes out, and the inner wheel side toes in.
Thereafter, upon lateral force increasing, and also a suspension stroke starting to generate lateral force compliance steer and bump steer, finally the outer wheel side has a tendency to toe in, and the inner wheel side has a tendency to toe out, but steering stability is deteriorated by the rear wheels being steered to the inverse phase temporarily at an early stage of turning.